Actuator

ABSTRACT

An actuator which makes it possible to avoid adhesion of dust or the like to a driving force-transmitting member, wipe out the fear of stop or breakage thereof, and avoid leakage of dust or the like to the outside. Fixing blocks 26a, 26b are slidably provided via guide blocks 22a to 22d on guide rails 18a, 18b for constructing an actuator 10. Slits 88a, 88b are defined at gaps between a top cover 84 and side covers 82a, 82b. Seal members 94a, 94b are provided for each of the slits 88a, 88b. A forward end of one of the seal members 94b is engaged with a step section 104a or 104b of the other seal member 94a to close the slit 88a, 88b. The fixing blocks 26a, 26b penetrate and protrude through the slits 88a, 88b. The forward ends of the seal members 94a, 94b abut against wall portions of the fixing blocks 26a, 26b to close the gaps disposed at the passages into the inside of the actuator 10.

TECHNICAL FIELD

The present invention relates to an actuator for transporting aworkpiece by transmitting a rotary driving force of a rotary drivingsource to a slider by the aid of a driving force-transmitting meansprovided on a main actuator body so that the slider is displaced.

BACKGROUND ART

An actuator has been hitherto used as a means for transporting aworkpiece. The actuator basically comprises a rotary driving sourcearranged at the inside of a housing of the actuator, a drivingforce-transmitting means such as a ball screw for converting the rotarydriving force of the rotary driving source into rectilinear motion to betransmitted to another member, and a slider for making displacementalong the longitudinal direction of the actuator by the aid of thedriving force-transmitting means.

The slider makes displacement along an opening of the housing, and ittransmits the rotary motion of the rotary driving source disposed in thehousing to the outside of the housing as the rectilinear motion.

However, the conventional actuator involves the following fear dependingon the environment in which the actuator is used. That is, for example,dust, water, water vapor, coolant, cutting fluid, and grinding fluidmake invasion through the opening of the housing, and they adhere to thedriving force-transmitting means. When the actuator is driven, the dustor the like is caught in the gap between the driving force-transmittingmeans and the slider, resulting in stop or breakage of the actuator.Further, the following problem is pointed out. That is, when theactuator is used at a place to be prevented from dust or the like, suchas those relevant to the medical field, those relevant to the field offood, and clean rooms, any leakage occurs from the actuator to theoutside, concerning, for example, the dust and the grease used for themotor, the ball screw, the bearing and the like for constructing thedriving force-transmitting means and the rotary driving source.

This invention has been made in order to solve the problems describedabove, an object of which is to provide an actuator which makes itpossible to avoid adhesion of dust or the like to a drivingforce-transmitting means, wipe out the fear of stop or breakage or thelike of the driving force-transmitting means, and avoid leakage of dustor the like to the outside.

DISCLOSURE OF THE INVENTION

In order to achieve the object described above, the present inventionlies in an actuator for converting rotary motion of a rotary drivingsource into rectilinear motion by the aid of a drivingforce-transmitting means to move a workpiece by using a slider whichmakes displacement in accordance with an action of the rectilinearmotion, the actuator comprising:

a housing for accommodating the rotary driving source and the drivingforce-transmitting means therein;

the slider which has a part protruding outwardly through an opening ofthe housing, for making the displacement by the aid of the drivingforce-transmitting means; and

a seal member which is flexibly formed of an elastic material and whichis provided to close the opening, wherein:

a part of the opening to be closed by the seal member is opened by theslider protruding through the opening.

According to the present invention, the opening is closed by the sealmember. When the rotary driving source is operated, then the rotarymotion of the rotary driving source is converted into the rectilinearmotion by means of the driving force-transmitting means, and the slideris displaced. The seal member is pressed by the slider, and it is bentoutwardly with respect to the opening. The seal member abuts against thewall of the slider to avoid invasion and leakage of dust or the likethrough the opening.

In a preferred embodiment, the seal member comprises a pair of elasticmembers, and step sections are formed at portions of the respectiveelastic members opposing to one another. When a forward end of one ofthe elastic members is engaged with the step section of the other whenthe opening is closed, the respective elastic members make abutment is awell-suited manner. Thus, it is possible to appropriately avoid invasionand leakage of dust or the like.

In another preferred embodiment, the elastic member is formed with aplurality of step sections. When the forward end of one of the elasticmembers is engaged with any one of the step sections of the other, theseal member can close the opening more reliably. Thus, it is possible tomore appropriately avoid invasion and leakage of dust or the like.

In still another preferred embodiment, a wedge-shaped section is formedat an end of the slider in a displacement direction. When the sealmember is flexibly bent by an end of the wedge-shaped section, no gap isformed between the seal member and the end of the slider in thelongitudinal direction. Thus, it is possible to avoid invasion andleakage of dust or the like, which is preferable.

In still another preferred embodiment, the wedge-shaped section isformed of ultrahigh molecular weight polyethylene. In this embodiment,the friction is decreased between the wedge-shaped section and the sealmember, which is more preferable.

In still another preferred embodiment, the slider comprises a pair offixing blocks which are provided substantially in parallel to oneanother, and parts of the fixing blocks protrude outwardly through thepair of openings defined for the housing. In this embodiment, the slidercan be stably supported by the pair of fixing blocks, which ispreferable.

In still another preferred embodiment, the fixing block is formed ofCFRP. In this embodiment, the fixing block can be formed to have a thinwidth. Therefore, it is possible to decrease the displacement amount ofthe seal member which is pressed and flexibly bent by the fixing block.Thus, it is possible to more appropriately avoid invasion and leakage ofdust or the like.

In still another preferred embodiment, the rotary driving source is amotor. In this embodiment, it is possible to obtain an electric actuatorcapable of avoiding invasion and leakage of dust or the like.

In still another preferred embodiment, the driving force-transmittingmeans comprises:

a ball screw connected to the rotary driving source; and

an engagement block secured to the slider and rotatably attached to theball screw, wherein:

rotation of the ball screw allows the engagement block to makedisplacement integrally with the slider in an axial direction of theball screw. In this embodiment, it is possible to obtain the actuatorhaving a simple structure, which is more preferable.

In still another preferred embodiment, the housing comprises:

a frame;

end covers provided at both ends of the frame;

side covers provided at side surface sections of the frame; and

a top cover provided at an upper surface section of the frame, wherein:

the opening is formed at a gap between the top cover and the side cover.In this embodiment, it is unnecessary to use any exclusive member forforming the opening. Thus, it is possible to reduce the production costof the actuator, which is preferable.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a perspective view illustrating an actuator according to anembodiment of the present invention;

FIG. 2 shows an exploded perspective view illustrating principal partsof the actuator shown in FIG. 1;

FIG. 3 shows a sectional view of the actuator taken along a lineIII--III shown in FIG. 1;

FIG. 4 shows a sectional view of the actuator taken along a line IV--IVshown in FIG. 1;

FIG. 5 shows a partial sectional view illustrating a motor section forconstructing a driving unit of the actuator shown in FIG. 1;

FIG. 6 shows a partial sectional view illustrating an encoder sectionfor constructing the driving unit of the actuator shown in FIG. 1;

FIG. 7 shows a partial magnified sectional view illustrating theactuator shown in FIG. 3;

FIG. 8 shows a partial magnified plan view illustrating the actuatorshown in FIG. 1;

FIG. 9 shows a perspective view illustrating an actuator system to whichthe actuator according to the embodiment of the present invention isapplied;

FIG. 10 shows actuators concerning other embodiments of the presentinvention;

FIG. 10A shows a partial magnified plan view illustrating the actuatorwith a circumferential surface of a wedge-shaped section of a sliderformed to have a convex configuration;

FIG. 10B shows a partial magnified plan view illustrating the actuatorwith a circumferential surface of a wedge-shaped section of a sliderformed to have a concave configuration;

FIG. 11 shows a longitudinal sectional view of an actuator concerninganother embodiment of the present invention; and

FIG. 12 shows a longitudinal sectional view of an actuator concerningstill another embodiment of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION

The actuator according to the present invention as exemplified bypreferred embodiments will be explained in detail below with referenceto the accompanying drawings.

With reference to FIGS. 1 and 2, reference numeral 10 indicates anactuator according to an embodiment of the present invention. Theactuator 10 comprises a lengthy frame 12 formed to have an approximatelyU-shaped cross section. As shown in FIG. 3, the frame 12 has, at itslower portion, through-holes 14a to 14d formed to have approximatelyrectangular cross sections. The through-holes 14a to 14d are used, forexample, as passages for wiring led to a motor described later on.Grooves 16a, 16b, which extend along the longitudinal direction, andeach of which has an approximately T-shaped cross section, are definedat the bottom surface of the frame 12 so that unillustrated fixingmembers are inserted thereinto in order to connect the actuator, forexample, to another apparatus.

Guide rails 18a, 18b are formed at the upper portion of the frame 12 toextend substantially in parallel to one another. The guide rails 18a,18b have slant surfaces 20a, 20b respectively. As shown in FIG. 3, theguide rails 18a, 18b are formed to have a wide width at their upperportions. Guide blocks 22a to 22d, which are slidable along thelongitudinal direction of the guide rails 18a, 18b, are disposed on therespective guide rails 18a, 18b. Inclined sections 23a, 23b are formedfor the guide blocks 22a to 22d. The inclined sections 23a, 23b areengaged with the slant surfaces 20a, 20b. Thus, the guide blocks 22a to22d are prevented from disengagement. Unillustrated rolling members suchball bearings are arranged at sliding portions between the guide rails18a, 18b and the guide blocks 22a to 22d. Accordingly, the guide blocks22a to 22d can be smoothly displaced along the guide rails 18a, 18b.

A pair of fixing blocks 26a, 26b for constructing a slider 24 arefastened by screws and fixed on the guide blocks 22a to 22d such thatthey are separated from each other by a predetermined spacing distanceand they are substantially parallel to one another (see FIGS. 2 and 3).A holding block 28 having an approximately rectangular configuration isintegrally connected between the fixing blocks 26a, 26b. A circular hole30 is defined through the holding block 28. For example, anunillustrated table member may be secured to the fixing blocks 26a, 26bby using screw holes 29 to be fastened with screws. Reference numeral 31in the drawing indicates a groove to be used for positionaldetermination when the unillustrated table member or the like is securedto the fixing blocks 26a, 26b.

As shown in FIGS. 2 and 4, step sections 32, 34 are formed at both endsof the frame 12. A driving unit 36 is fixed on the step sections 32, 34.The driving unit 36 comprises a ball screw 38, a motor section 40 and anencoder section 42 which are provided coaxially at both ends of the ballscrew 38 respectively, and an engagement block 44 which is rotatablyattached to the ball screw 38 to make displacement along the axialdirection, wherein the ball screw 38, the motor section 40, the encodersection 42, and the engagement block 44 are integrated into one unit.The engagement block 44 is provided with a column section 46. The columnsection 46 is installed into the hole 30 of the holding block 28 by theaid of attachment holes 48. Alternatively, an unillustrated timing beltmay be used in place of the ball screw 38 which functions as a feedscrew.

As shown in FIG. 5, the motor section 40 is fixed on the step section 32of the frame 12 by the aid of screws 50. The motor section 40 includes amotor-fixing block 52 which is positioned at the center of the frame 12by inserting an unillustrated positioning pin, and a casing 54 having anapproximately rectangular cross section to be integrally joined to themotor-fixing block 52. A stator 56 is provided at the outercircumference portion of the casing 54. A stator coil section 58 isprovided with a coil wound around at the inner wall surface of thestator 56. A shaft section 38a, which continues to the terminal end ofthe ball screw 38 and which extends along the axial direction, isrotatably supported by a bearing member 60 in the casing 54. A rotor 62is held by the shaft section 38a by the aid of a set screw 64.

As shown in FIG. 6, the encoder section 42 comprises an encoder-fixingblock 70 for rotatably supporting a shaft section 38b continued to theball screw 38 by the aid of a bearing member 66, the encoder-fixingblock 70 being fixed to the step section 34 of the frame 12 by the aidof screws 68, and a main encoder body 76 for detecting, for example, thenumber of rotation or the angle of rotation of the ball screw 38, themain encoder body 76 being connected to the encoder-fixing block 70 bythe aid of connecting members 72, 74. Detection signals concerning, forexample, the number of rotation or the angle of rotation, which aregenerated by the main encoder body 76, are introduced into anunillustrated controller via a lead wire 77.

As shown in FIG. 2, the driving unit 36 is fixed by positioning andfixing the motor section 40 and the encoder section 42 on the stepsections 32, 34 defined at the both ends of the frame 12 respectively.Thus, the parallel accuracy can be secured for the ball screw 38 and theguide rails 18a, 18b. Further, unillustrated positioning pins areinserted into positioning holes (not shown) defined in the motor-fixingblock 52 and the encoder-fixing block 70 respectively, and intopositioning holes 78 defined in the step sections 32, 34 of the frame 12respectively. Thus, the motor-fixing block 52 and the encoder-fixingblock 70 can be positioned at the center of the frame 12 respectively.

The driving unit 36 comprises the motor section 40, the ball screw 38,and the encoder section 42 as one unit. However, for example, only themotor section 40 and the ball screw 38 may be constructed as a unit byusing an unillustrated pulse motor such as a stepping motor.

It is also possible to adopt an arrangement in which the encoder-fixingblock 70 is provided with a sensor such as a limit switch in place ofthe main encoder body 76.

As shown in FIG. 4, a pair of end covers 80a, 80b, which are opposed toone another, are installed at both ends of the frame 12 along thelongitudinal direction respectively. As shown in FIG. 3, a pair of sidecovers 82a, 82b, which are opposed to one another, are installed at bothside surfaces of the frame 12 along the transverse directionrespectively. A top cover 84 is installed at the upper surface of theframe 12. The housing of the actuator 10 is constructed by the frame 12,the end covers 80a, 80b, the side covers 82a, 83b, and the top cover 84.

Slits (openings) 88a, 88b are defined at gaps between the top cover 84and the side covers 82a, 82b, which extend along the longitudinaldirection of the frame 12. As shown in FIG. 7, grooves 90a, 90b aredefined at wall portions facing to each of the slits 88a, 88b betweenthe top cover 84 and each of the side covers 82a, 82b. Projections 92a,92b are formed in the vicinity of the opening, adjacent to the grooves90a, 90b. Edges of a pair of seal members 94a, 94b are inserted into thegrooves 90a, 90b, each of the seal members 94a, 94b being formed to havea lengthy plate-shaped configuration.

The pair of seal members 94a, 94b are separated from each other alongthe displacement direction of the slider 24. Each of the seal members94a, 94b is formed of a material having elasticity such as naturalrubber and synthetic rubber. An engaging section 96a, 96b, which isformed to be thick, is provided at the edge of the seal member 94a, 94b.A projection 98a, 98b, which is formed at the engaging section 96a, 96balong the edge, is engaged with the projection 92a, 92b of the groove90a, 90b. Thus, the seal member 94a, 94b is prevented from disengagementfrom the groove 90a, 90b. A flexible bending section 100a, 100b, whichis formed to be thin, is continued to the engaging section 96a, 96b.

A closing section 102a, 102b is further formed continuously to theflexible bending section 100a, 100b. The closing section 102a, 102b isformed such that its thickness is gradually increased as the spacingdistance from the flexible bending section 100a, 100b is increased. Stepsections 104a, 104b are formed on the lower surface of the closingsection 102a as shown in the drawing. On the other hand, step sections104c, 104d are formed on the lower surface of the closing section 102b.The forward end of the first closing section 102b is engaged with thestep section 104a or the step section 104b of the second closing section102a, and they make tight contact with each other owing to theelasticity of the material for forming the seal members 94a, 94b. Theseal members 94a, 94b are arranged in a roof-shaped configuration toclose the slit 88a, 88b. Although not shown, even when the forward endof the second closing section 102a is engaged with the step section 104cor the step section 104d of the first closing section 102b, it is alsopossible to close the slit 88a, 88b.

The fixing blocks 26a, 26b for constructing the slider 24 penetratethrough the slits 88a, 88b, and they protrude upwardly as shown in thedrawing. Thus, the rectilinear motion effected in the housing in theactuator 10 is transmitted to the outside of the actuator 10. Therespective closing sections 102a, 102b of the seal members 94a, 94b arepressed by the fixing block 26a, 26b, and they are displaced outwardlyfrom the slit 88a, 88b as shown by two-dot chain lines in FIG. 7. Duringthis process, the forward ends of the closing sections 102a, 102b abutagainst the wall portions of the fixing block 26a, 26b by the aid of theelasticity of the material for constructing the seal members 94a, 94b.Thus, the closed state is maintained at the gap disposed at the passageinto the inside of the actuator 10.

The actuator 10 according to the embodiment of the present invention isbasically constructed as described above. Next, its operation, function,and effect will be explained.

The motor section 40 is driven by operating the unillustrated powersource to rotate the ball screw 38 which functions as the motor shaft.In this embodiment, for example, the number of rotation or the angle ofrotation of the motor is detected by the main encoder body 76 providedat the end of the ball screw 38. The detected signal is introduced intothe unillustrated controller via the lead wire 77 inserted into any oneof the through-holes 14a to 14d.

The rotational motion of the ball screw 38 is transmitted to theengagement block 44 rotatably attached to the ball screw 38, and it isconverted into the rectilinear motion. Thus, the slider 24, which holdsthe engagement block 44, is displaced smoothly and linearly along theguide rails 18a, 18b.

During this process, the seal members 94a, 94b are gradually displacedoutwardly with respect to the slit 88a, 88b, and they are separated fromeach other on the front side in the travelling direction of the slider24 by being pressed by the fixing block 26a, 26b, from the state inwhich the seal members 94a, 94b make tight contact in the roof-shapedconfiguration to close the slit 88a, 88b as shown by solid lines in FIG.7. As a result, the forward ends of the closing sections 102a, 102b areopened along the wall portions of the fixing block 26a, 26b as shown bytwo-dot chain lines in FIG. 7. On the other hand, the seal members 94a,94b are gradually displaced on the opposite side in the travellingdirection of the slider 24 owing to the elasticity of the seal members94a, 94b, from the state in which the seal members 94a, 94b slidablycontact with the wall portions of the fixing block 26a, 26b. The forwardend of the first seal member 94 is engaged with the step section 104a ofthe second seal member 94a to make tight contact in the roof-shapedconfiguration. In this embodiment, as shown in FIG. 8, the closed stateis maintained for the slits 88a, 88b, regardless of the presence orabsence of the fixing blocks 26a, 26b. Thus, the actuator 10 isprevented from invasion of dust or the like into the inside of theactuator 10 and from leakage of dust, grease, or the like from theactuator 10 to the outside.

It is also assumed that the forward end of the first closing section102b fails to make engagement with the step section 104a disposed at theforward end side of the second closing section 102a. In such a case, theengagement with the other step section 104b makes it possible to closethe slits 88a, 88b. Accordingly, the integral formation of the pluralityof step sections 104a, 104b on the seal members 94a, 94b makes itpossible to more reliably close the slits 88a, 88b and avoid invasionand leakage of dust or the like. It is a matter of course that theforward end of the seal member 94a may be engaged with the step section104c or the step section 104d of the seal member 94b.

The internal space of the actuator 10 may be allowed to communicate witha vacuum suction source, for example, via the through-holes 14a to 14ddefined in the frame 12 to draw the interior air from the actuator 10together with dust or the like. By doing so, the actuator 10 can be moreappropriately prevented from leakage of dust or the like therefrom tothe outside.

FIG. 9 shows an actuator system 110 to which the actuator 10 accordingto the embodiment of the present invention is applied. The actuatorsystem 110 includes frames constructed by a plurality of columnarmembers 112 for forming the system 110. A first actuator 10a is securedto one of the columnar members 112. A second actuator 10b is attached toa slider 24a of the first actuator 10a so that it extends in a directionperpendicular to the displacement direction of the slider 24a. Acylinder 118, to which an attracting unit 116 is installed, is attachedto a slider 24b of the second actuator 10b. The first actuator 10a, thesecond actuator 10b, the cylinder 118, and the attracting unit 116 areelectrically connected to a controller 120 via cables 124a, 124b. Thecontroller 120 is electrically connected to a control panel 122.

When an operator operates the control panel 122 of the actuator system110 constructed as described above, the first actuator 10a, the secondactuator 10b, the cylinder 118, and the attracting unit 116 are operatedin a predetermined manner on the basis of the control command given bythe controller 120. For example, an unillustrated workpiece, which istransported between the frames, is subjected to working operation suchas attraction and transfer.

It is noted that the slits 88a, 88b of the first actuator 10a and thesecond actuator 10b are closed by the seal members 94a, 94b. Therefore,the first actuator 10a and the second actuator 10b are free from thefear of invasion of dust or the like thereinto to stop or break theactuator system 110. Further, the first actuator 10a and the secondactuator 10b are free from the fear of leakage of dust or the liketherefrom to contaminate the interior of the room in which the actuatorsystem 110 is arranged. Therefore, the actuator system 110 can be usedat a place to be prevented from dust or the like, such as those relevantto the medical field, those relevant to the field of food, and cleanrooms.

In the foregoing embodiments, the fixing blocks 26a 26b are formed tohave the rectangular cross-sectional configuration. However, as shown inFIGS. 10A and 10B, the end in the displacement direction of the fixingblock 26a, 26b may be made gradually thin to form a wedge-shaped section130a or a wedge-shaped section 130b. In this embodiment, when the sealmembers 94a, 94b make displacement at front and rear portions in thetravelling direction of the slider 24 in accordance with thedisplacement of the slider 24, the forward ends of the closing sections102a, 102b are disposed along wedge-shaped wall portions of the fixingblock 26a, 26b. Accordingly, the gap, which is disposed at the passageinto the inside of the actuator 10, is further decreased. Thus, it ispossible to more appropriately avoid invasion and leakage of dust or thelike. In this embodiment, the circumferential configuration of thewedge-shaped section 130a may be convex as shown in FIG. 10A.Alternatively, the circumferential configuration of the wedge-shapedsection 130b may be concave as shown in FIG. 10B. When the wedge-shapedsections 130a, 130b are formed of a synthetic resin such as ultrahighmolecular weight polyethylene (UHMWPE), the friction is preferablydecreased with respect to the seal members 94a, 94b.

When grease or the like is applied to the seal members 94a, 94b, thenthe respective seal members 94a, 94b make tight contact moreappropriately, and it is possible to obtain further smooth operation ofthe slider 24.

When a material such as CFRP is used for the fixing blocks 26a, 26b,then the width of the fixing blocks 26a, 26b can be formed to be thin,and the displacement amount of the seal members 94a, 94b can bedecreased. Thus, it is possible to more appropriately avoid invasion andleakage of dust or the like.

In the foregoing embodiments, the two slits 88a, 88b are used. However,it is allowable to use one slit or three or more slits. In such anembodiment, a pair of seal members 94a, 94b are provided for each slit.

Alternatively, as shown in FIG. 11, one guide rail 18c having a widewidth may be formed at an upper portion of a frame 12 so that one guideblock 22e having a wide width may slide thereon. Further alternatively,as shown in FIG. 12, a frame 12 and guide rails 18d, 18e are formed byusing different members so that they are secured to one another by usingunillustrated screws or the like.

The present invention is also applicable to electromagnetic linearactuators, pneumatic linear actuators, pneumatic cylinders, andactuators described in Japanese Laid-Open Patent Publication Nos.6-197491, 7-110057, and 6-222816 filed by the present applicant, as wellas structures or systems constructed by using such actuators.

According to the actuator concerning the embodiment of the presentinvention, the opening of the actuator is closed by the seal members.Accordingly, the driving force-transmitting means is prevented fromadhesion of dust or the like. Therefore, it is possible to avoid thefear of stop or breakage of the actuator, which would be otherwisecaused by dust or the like caught into the actuator. It is possible toeffect the stable transport function for the workpiece, making it easyto maintain and manage the actuator. Further, the seal members make itpossible to exclude leakage of dust, grease or the like from the insideof the actuator. Accordingly, the actuator can be used, for example, forthose relevant to the medicine, those relevant to the food, and cleanrooms.

The plurality of step sections are formed at the mutually opposingportions of the pair of seal members. Accordingly, the opening isreliably closed by engaging the forward end of the first seal memberwith the step section of the second seal member. Thus, it is possible tomore appropriately avoid invasion and leakage of dust or the like.

When the wedge-shaped section is formed at the end of the slider toavoid the formation of the gap between the seal members and the end inthe longitudinal direction of the slider, the opening can be closed morereliably. When the wedge-shaped section is formed of ultrahigh molecularweight polyethylene, it is possible to decrease the friction between thewedge-shaped section and the seal members, which is preferable.

The slider can be stably supported by the pair of fixing blocks providedsubstantially in parallel to one another for the slider. When the fixingblocks are formed of CFRP, then the width of the fixing blocks can beformed to be thin, and it is possible to decrease the displacementamount of the seal members pressed and flexibly bent by the fixingblocks. Thus, it is possible to more appropriately avoid invasion andleakage of dust or the like.

When the motor is used for the rotary driving source, it is possible toobtain the electric actuator capable of avoiding invasion and leakage ofdust or the like. In this embodiment, when the drivingforce-transmitting means is based on the use of the ball screw and theengagement block provided for the slider and rotatably attached to theball screw, the actuator can be conveniently constructed.

When the housing is constructed by the frame, the end covers, the sidecovers, and the top cover, and the opening is formed at the gap betweenthe top cover and the side cover, then it is unnecessary to use anyexclusive member for forming the opening.

INDUSTRIAL APPLICABILITY

As described above, the actuator according to the present invention isappropriately usable to transport the workpiece or the like, forexample, on the production line arranged in factories which frequentlyinvolve dust, water, water vapor, coolant, cutting fluid, grinding fluidand the like, and in factories to be prevented from dust or the like,such as those relevant to the medical field, those relevant to the fieldof food, and clean rooms.

We claim:
 1. An actuator for converting rotary motion of a rotarydriving source (40) into rectilinear motion by the aid of a drivingforce-transmitting means (38, 44) to move a workpiece by using a slider(24) which makes displacement in accordance with an action of saidrectilinear motion, said actuator comprising:a housing (12, 80a, 80b,82a, 82b, 84) for accommodating said rotary driving source (40) and saiddriving force-transmitting means (38, 44) therein; said slider (24)which has a part protruding outwardly through an opening (88a, 88b) ofsaid housing (12, 80a, 80b, 82a, 82b, 84), for making said displacementby the aid of said driving force-transmitting means; and a seal member(94a, 94b) which is flexibly formed of an elastic material and which isprovided to close said opening (88a, 88b), wherein:a part of saidopening (88a, 88b) to be closed by said seal member (94a, 94b) is openedby said slider (24) protruding through said opening (88a, 88b).
 2. Theactuator according to claim 1, wherein said seal member (94a, 94b)comprises a pair of elastic members having step sections (104a, 104b,104c, 104d) formed at opposing portions respectively, and a forward endof one of said elastic member s is engaged with any of said stepsections (104a, 104b, 104c, 104d) of the other when said opening (88a,88b) is closed.
 3. The actuator according to claim 2, wherein saidelastic member is formed with a plurality of step sections (104a, 104b,104c, 104d), and said forward end of one of said elastic members isengaged with any one of said step sections (104a, 104b, 104c, 104d) ofthe other.
 4. The actuator according to claim 1, wherein a wedge-shapedsection (130a, 130b) is formed at an end of said slider (24) in adisplacement direction, and said seal member (94a, 94b) is flexibly bentby an end of said wedge-shaped section (130a, 130b).
 5. The actuatoraccording to claim 4, wherein said wedge-shaped section (130a, 130b) isformed of ultrahigh molecular weight polyethylene.
 6. The actuatoraccording to claim 1, wherein said slider (24) comprises a pair offixing blocks (26a, 26b) which are provided substantially in parallel toone another, and parts of said fixing blocks (26a, 26b) protrudeoutwardly through said pair of openings (88a, 88b) defined for saidhousing (12, 80a, 80b, 82a, 82b, 84).
 7. The actuator according to claim6, wherein said fixing block (26a, 26b) is formed of CFRP.
 8. Theactuator according to claim 1, wherein said rotary driving source is amotor (40).
 9. The actuator according to claim 1, wherein said drivingforce-transmitting means comprises:a ball screw (38) connected to saidrotary driving source (40); and an engagement block (44) secured to saidslider (24) and rotatably attached to said ball screw (38),wherein:rotation of said ball screw (38) allows said engagement block(44) to make displacement integrally with said slider (24) in an axialdirection of said ball screw (38).
 10. The actuator according to claim1, wherein said housing (12, 80a, 80b, 82a, 82b, 84) comprises:a frame(12); end covers (80a, 80b) provided at both ends of said frame (12);side covers (82a, 82b) provided at side surface sections of said frame(12); and a top cover (84) provided at an upper surface section of saidframe (12), wherein:said opening (88a, 88b) is formed at a gap betweensaid top cover (84) and said side cover (82a, 82b).